Update installation instructions.

[HarryAddison]

Installation using pip3 install astronify fails:

pip3 install astronify
Collecting astronify
Downloading astronify-0.1.tar.gz (2.5 MB)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 2.5/2.5 MB 14.5 MB/s eta 0:00:00
Installing build dependencies ... done
Getting requirements to build wheel ... done
Preparing metadata (pyproject.toml) ... done
ERROR: Could not find a version that satisfies the requirement thinkx (from astronify) (from versions: none)
ERROR: No matching distribution found for thinkx

It appears that thinkx is no longer available through PyPi and should be installed from source (https://github.com/AllenDowney/ThinkX?tab=readme-ov-file).

[scfleming]

Thanks I encountered this issue too, and found the same thing. I am not sure Astronify actually needs that package, so if you need to install before a new version of Astronify is released, you can try removing that from the setup.cfg and install from source. As soon as I can I want to try this myself, but am swamped at the moment.

[folsomcp]

I just ran into that issue with tinkx too. It's possible to install directly from their github, e.g.:
pip install "git+https://github.com/AllenDowney/ThinkX.git"
But it seems like that github repo hasn't been updated in 7 years, so it would be nicer to not depend on.

[scfleming]

Yeah, I have a work-in-progress branch, "py311", that removes this as a dependency.